my friend was trying to hard wire his radar detector into his accord by splicing it and putting it into his cigar lighter fuse in the fusebox and grounding the black wire. well he must've mixed them up because he had it working fine but he switched it to another fuse and reversed the wires accidentally and now it doesn't work at all. is it fried or can it be fixed?

 

The fuse should have blown, but if he didn't have it fused, then he may have an issue.

Depending on make/model of radar detector, they're sometimes not worth fixing.